// scrollLoader.vue
// 滚动加载组件

<style scoped>
   .container-main {margin: 0 auto; overflow: auto; overflow-x: hidden; padding: 0;}
   .loading{ width: 100%; height: 40px; position: relative; overflow: hidden; text-align: center; margin: 5px 0 ; color: #999; font-size: 13px;}
   .loading-icon{color: #707070;};
   .loader {
        font-size: 10px;
        margin: 8px auto;
        text-indent: -9999em;
        width: 24px;
        height: 24px;
        border-radius: 50%;
        background: #999;
        background: -moz-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
        background: -webkit-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
        background: -o-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
        background: -ms-linear-gradient(left, #999 10%, rgba(255, 255, 255, 0) 42%);
        background: linear-gradient(to right, #999 10%, rgba(255, 255, 255, 0) 42%);
        position: relative;
        -webkit-animation: load3 1s infinite linear;
        animation: load3 1s infinite linear;
    }
    .loader:before {
        width: 50%;
        height: 50%;
        background: #999;
        border-radius: 100% 0 0 0;
        position: absolute;
        top: 0;
        left: 0;
        content: '';
    }
    .loader:after {
        background: #f5f5f5;
        width: 72%;
        height: 75%;
        border-radius: 68%;
        content: '';
        margin: auto;
        position: absolute;
        top: 0;
        left: 0;
        bottom: 0;
        right: 0;
    }
    @-webkit-keyframes load3 {
    0% {
        -webkit-transform: rotate(0deg);
        transform: rotate(0deg);
    }
    100% {
        -webkit-transform: rotate(360deg);
        transform: rotate(360deg);
    }
    }
    @keyframes load3 {
    0% {
        -webkit-transform: rotate(0deg);
        transform: rotate(0deg);
    }
    100% {
        -webkit-transform: rotate(360deg);
        transform: rotate(360deg);
    }
    }
</style>

<template>
    <div id="scrollLoader-container" class="container-main">
        <div class="loading" v-if="topLoading">
            <div class="loader">加载中...</div>
        </div>

        <div :style="'min-height:' + realMinHeight + 'px; overflow-x:hidden'">
            <slot></slot>
        </div>

        <div class="loading" v-if="bottonLoading">
            <div class="loader">加载中...</div>
        </div>
    </div>
</template>

<script>
    export default {
        name: "scroll-loader",
        
        props: {
            //给slot传一个最小值，保证一开始能出现滚动条
            'minHeight': {
                type: Number,
                default: 800
            }, 
                
        },
        created(){
        },
        computed: {
            realMinHeight(){
                return this.minHeight + 30
            }
        },
        data() {
            return {
               topLoading: false,
               bottonLoading: false,
               stopTopLoading: false, //是否停止传播滚动到顶部事件
               stopBottonLoading: false,  //是否停止传播滚动到底部事件
            }
        },
        mounted(){
            this.listenScroll();
        },
        methods: {
            listenScroll(){
                var me = this;
                var topDone = (stopTopLoading) => {
                    me.topLoading = false;
                    if(stopTopLoading) me.stopTopLoading = true;
                };
                var bottonDone = (stopBottonLoading) => {
                    me.bottonLoading = false;
                    if(stopBottonLoading) me.stopBottonLoading = true;
                };
                setTimeout(function(){
                    var scrollContainer = document.getElementById('scrollLoader-container');
                    scrollContainer.onscroll = function(){
                        if(scrollContainer.scrollTop<=0 && !me.stopTopLoading){
                            if(me.topLoading) return;
                            me.topLoading = true;
                            me.$emit('scroll-to-top', topDone);
                        }
                        if((scrollContainer.offsetHeight + scrollContainer.scrollTop+1 >= scrollContainer.scrollHeight) && !me.stopBottonLoading){
                            if(me.bottonLoading) return;
                            me.bottonLoading = true;
                            scrollContainer.scrollTop += 40;
                            me.$emit('scroll-to-botton', bottonDone);
                        }
                    }
                }, 50)
            },
        }
    }
</script>